Conventionally, a processing technique of this kind has been performed in the following manner as in Patent Document 1. A flange portion is formed on a midway part of a shaft body as shaft caulking, and a circular hole is punched on a plate-like body which is a press component as a subject of assembly. A tip of the shaft body which is inserted through the circular hole is crushed by a caulking machine for exclusive use so that the press component is sandwiched between the crushed head part of the shaft body and the flange portion to thereby assemble the shaft body with the plate-like body. Alternatively, a more complicated special shape is previously formed on the shaft body, and the shaft body is press-fitted into the circular hole formed in the press component to thereby join the shaft body to the press component.
However, a large flange portion needs to be provided on the midway part of the shaft body in order to sandwich the press component between the crushed head part of the shaft body and the flange portion. Accordingly, it is necessary to cut a shaft material that is approximately 50% thicker than a shaft diameter required for using as a product to produce a flange shape, which increases material and processing costs. Further, a high manufacturing cost is required also for forming the special shape, which limits the cost reduction.
In view of the above, there has also been proposed a caulking method in which a mounting hole for inserting and assembling a columnar body is provided in a metallic plate-like body, a thick portion is formed along an inner circumferential edge of the mounting hole by burring, a circumferential groove having a predetermined depth is formed at an assembly position on an outer circumferential surface of the columnar body to be inserted into the mounting hole, the columnar body is inserted into the mounting hole of the metallic plate-like body so as to be set in an assembly position where the thick portion and the circumferential groove face each other, and the thick portion is compressively pressed from an axial direction of the columnar body so as to be plastically deformed toward the center of the mounting hole to thereby cause the thick portion to bite into the facing circumferential groove of the columnar body (see Patent Document 2 and Patent Document 3).
In this method, it is not necessary to provide a flange portion on the midway part of the columnar body or produce a complicated special shape. Therefore, this method makes it possible to assemble the plate-like body with the columnar body by caulking by easy press working as well as at a low cost only by providing the circumferential groove which can be easily formed in the columnar body and providing the thick portion on the periphery of the mounting hole of the plate-like body by burring. Further, since the thick portion is formed on the plate-like body, and then plastically deformed so as to bite into the circumferential groove, it is possible to obtain sufficient caulking strength as well as the strength of the plate-like body itself. Therefore, it is possible to achieve an effect that, even if the plate-like body is thinner than a conventional plate-like body, the same high caulking strength as that of the conventional one can be obtained.